# `UNAUTHENTICATED` Authentication failed

Source: https://checkslip.com/en/problems/unauthenticated

- **HTTP status**: `401`
- **Credit**: No credit taken

## Meaning

We could not tell who you are: the API key is not usable (malformed, revoked, expired or unknown), or the web-app session expired or was signed out. The exact case is not disclosed for security.

## Fix

API: send `Authorization: Bearer csk_…` with an active key. Web app: sign in again at app.checkslip.com.

## Example response

```
{
  "type": "https://checkslip.com/problems/unauthenticated",
  "title": "Authentication failed",
  "status": 401,
  "code": "UNAUTHENTICATED",
  "instance": "01a18600-0000-7000-8000-000000000000"
}
```